The overall objective of this research program is to enhance the precision and ease with which transcranial magnetic stimulation (TMS) can be used for the diagnosis and treatment of neurological and psychiatric disorders and for neuroscience research. This will be achieved through a coordinated program of technical developments, validations and theory-driven physiological experimentation which culminate in an aiming/holding robotic manipulandum for TMS (the TMS AHRM/TM; pronounced "arm"). The technical development program builds upon the capabilities of an FDA- approved neurosurgical robot (the NeuroMate), creating a new application for this device by extensive algorithmic developments and supportive mechanical developments. Algorithm developments target treatment planning and treatment delivery, including: algorithms for rapidly modeling the 3-D electric field created in the rain by a TMS coil at any external location; cortical surface modeling (extraction and visualization); scalar product (electric-field vector times cortical-surface vector) computation and visualization; and merging of functional images, structural images and treatment-planning models (surfaces & fields). Treatment-delivery tools include: frameless registration of head, brain image, and robot; fully automated robotic positions of the TMS coil; robotic sensing of TMS orientation (about a manually operated tool-rotation axis). Hardware extensions include: a passive digitizing arm, a TMS tool mount; a passive tool-rotation axis with an orientation sensor; and a general-purpose mobile cart. Technical validations measure the errors of each algorithm and procedure. Physiological validations test a new theory for modeling TMS local effects on the brain, called the Columnar Aiming Principles (CAPs). The technical development program will create an aiming/holding robotic manipulandum for TMS: the TMS AHRM/TM. The TMS AHRM/TM will greatly extend the capabilities of an FDA-approved medical robot, creating a prototype system for imaged-guided planning and robotic delivery for TMS. This prototype is intended for subsequent commercialization (e.g., through an SBIR award). In this proposal, a general aiming theory, the Columnar Aiming Principles (CAPs) for TMS will be validated. Collectively, these technical developments and physiological validations will create a system with wide potential for clinical and research applications.